Large wholesale processing machines which process photographically sensitized webs are well known. These machines can be run at speeds of up to 50 meters per minute depending on the number of tanks through which the web must pass to be processed. Further, such machines can be sufficiently wide to accommodate up to six separate webs moving in parallel through the machine. Most of these machines are individually configured from standard components to suit individual laboratory requirements.
Recent developments have shown that the chemical volume of the prior art large volume tank processing machines described above can be reduced by up to 90%. Such a low volume thin tank (LVTT) type apparatus is disclosed in U.S. Pat. Nos. 5,179,404; 5,311,235; 5,309,191; 5,339,131 and 5,387,499. A limit to the maximum practical volume reduction is dependent upon the space needed for reliable transport of the webs through the tanks and the efficient recirculation and/or replacement of the chemicals used in the tanks.
As a result of reducing the volumes of tanks in a processing apparatus, new chemical formulations (such as Redox Amplification (RX) formulations) can be used which shorten the time of the various processing steps occurring in the tanks, thereby leading to increases in the line speed of the processing apparatus.
In general, a photographic processing apparatus includes a continuous drive belt which follows the route of the photographically sensitized webs through the tanks of the apparatus to drive various rollers of the apparatus. To enable an end (or leader) of a photographically sensitized web to be carried through the tanks of the processing apparatus, it is normal to use a clip to join the end of the web to a drive belt such that the web travels with and in parallel to the drive belt through the processing tanks. The most common type of prior art leader clip is shown in FIG. 1.
The prior art clip shown in FIGS. 1A and 1B consists of two parts which are spot welded together. One part is a long arm defining a slot and the other part is a metal strip having ends which are bent to form claws for gripping a drive belt. In use, an end of a photographically sensitized web is folded through the slot and a drive belt is inserted between the claws of the clip. While these prior art clips are easy to attach to a moving drive belt, any drag occurring to the web causes the clip to be pulled out of square relative to the drive belt. If this occurs, as the clip passes around a top or bottom roller of the apparatus, bending of the clip can result. In most cases, some bending of the clip can be tolerated in a typical prior art large volume processing apparatus because there is room in the tanks to accommodate the effective increase in size of the clip. However, this is not the case in an LVTT processing apparatus and the clip may jam in the narrow processing channel defined between the rack and the tank and stop the machine.
The prior art clips shown in FIGS. 1A and 1B sometimes actually disengage from the drive belt within a tank of a processing apparatus. Although this results in causing waste product, if this occurs in a LVTT type apparatus it is also necessary to dismantle at least part of the machine to retrieve the clip immediately, since there is not sufficient room in a processing tank for a new clip to pass a clip lying at the bottom of the tank.
U.S. Pat. No. 4,279,371 discloses a one-piece hairpin-type holding element with two brackets welded to end portions of the element. Although the two brackets result in improved retention on a drive belt, the hairpin holding element does not define a closed slot spaced from the drive belt for photographically sensitized web. Further, the complete clip is too rigid for use in a LVTT type processing system since it has been found that the two brackets do not travel smoothly around a roller at the bottom of a processing tank.
Another known prior art type clip is shown in FIGS. 2A and 2B of the accompanying drawings. As can be seen, this clip is similar to that of FIGS. 1A and 1B, but has three claws for engaging a drive belt. Each claw is riveted or otherwise fastened to a flexible support which is riveted or otherwise fastened to the long arm part of the clip. This clip, however, is not entirely secure on a drive belt and often disengages, bends or moves out of square in a processing tank, resulting in jamming of the apparatus. It also suffers from an extra problem at the outlet end of the processing apparatus. In this regard, when a clip exits the last tank of the apparatus, the web is accumulated on a winder and it is necessary to remove automatically the clip from the drive belt. A wedge shaped finger is generally used, which slides between the drive belt and the clip causing the clip to disengage from the belt. However, the three claw clip of FIGS. 2A and 2B often only disengages from one claw and then twists diagonally on the belt and can cause damage.
As will be appreciated, a number of different types of leader clips are known. However, prior to the present invention, a truly satisfactory clip for use in a LVTT processing apparatus has not been known. The present invention provides such a clip.